Method of making tubing



. June 18, 1946. J. J. DUNN METHOD OF MAKING TUBING 2 Sheets-Sheet 'l Filed Aug. 23, 1945 M mi ' INVENTOR: JEPEY Jmf flu/v/v,

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June 18,- 1946. J. J. DUNN 7 2,402,383."

' r METHOD OF MAKING TUBING Filed Aug. 25, 1945 2 Sheets-Sheet 2 INVENTORI Jae/ r Jm flaw/v,-

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BYZ HIS -m ME.

Patented June 18,

Jen-y Jay Dunn, Ellwood City, Pa assignor to any, a corporation oi New National Tube Comp Jersey Application August 23, 1943, Serial No. 499,671

This invention relates to a method for improving the physical properties of tubular material, particularly the resistance to collapse of oil country goods such as casing, tubing and drill pipe.

In Patent No. 2,293,938 to Dunn et a1. there is discloseda cold-worked and heat-treated tubular article having a high resistance to collapse by reason of its stress-strain curve characteristics. It is there stated that the predetermination of the proper relation of the value of unit stress at the beginning of permanent deformation and its value at yield strength are of extreme importance in obtaining a stress-strain-curve having high collapse values. According to the disclosures thereof, the stress-strain curve of the material of the patented article is that in which the pro- 4 Claims. (01. 148,-12)

portional limit is at least 75% 0f the yield strength and the yield strength at least 75% of the tensile strength. The proportional limit" is therein defined as a test'wherein that value is associated with a permanent deformation of .01 The yield strength is the conventional .2% set value. These-same values will be used herein.

I have discovered that conventional cold straightening operations have a harmful effect on collapse resistance and it is an object of my invention to provide a method of making tubing wherein the disadvantages of cold straightening operations are not present.

The foregoing and other objects will be more apparent after referring to the following description and attached drawings, in which:

Figures 1 and 2, combined, disclose a mill layout for carrying out the method of the invention;

and

Figure 3 shows a roller type cooling table.

The tubular article of the present invention is 'made from a steel containing .15% to .50% car- 2 7 ing the heated billet through first and second piercing mills, reheating the billet, passing it through a Hi-Mill, reelers, and the sizing machine 2, all of which are shown in Figures 1 and 2. The tube is then cooled on'the'cooling table I and subjected to the conventional cold straightening operation.

A representative tube formed of the above steel by this conventional seamless tube practice, if allowed to cool to room temperature after being reeled and sized, has the following physical characteristics:

Tensile strength lbs, per sq, in..- 108,000 Yield strength -do 63,000 Proportional limit do.. 60,000 Elongation in 2" percent 26.8 Collapse pressure lbs. per. sq. in.-- 4,850

I have discovered that a tubular article having the desired physical characteristics can be obtained by a flnal finishing step in which the diameter of the tubular article is reduced at least 3% and preferably between 6 and 10% while at a temperature between the so-called blue-heat zone and somewhat below the lower critical temperature of the steel of which it is composed, preferably between 650 and 1000 for conventional grades of oil well casing steel, A temperature of about 850 hasbeen found to give good results.

Therefore, in accordance with the teachings of the present invention, the tube which is made about 8% oversize by conventional practice instead of being allowed to cool to room temperature after sizing, followed by a conventional bon, .25% to 2.00% manganese, and .50% maxiof steel of the following analysis: Per cent Carbon .40 Manganese 1.30 Silicon .22 Sulphur I .025 Phosphorous .030

cold straightening operation, is inserted after sizing in the recirculating furnace '0 and the temperature thereof equalized at a point between 650 and 1000 F., preferably at about 850 1'.

Following such equalization of temperature the tube is withdrawn from the furnace and quickly passed through a multi-stand set of sizing mill rolls 8 which are adjusted to reduce the diameter thereof about 8% and at the same time to straighten the tube; Upon emergence from the sinking or sizing mill 8, the tube is placed on a roller type cooling table l0 where it is rotated between successive steps thereover until it is sufficiently cooled to be placed upon a conventional cooling table without danger of uneven cooling, which causes out of roundness or warpwell supported along a straight line and there The conventional practice of forming a tube is heating billet to the desired temperature. passfore insure uniform cooling and maintain the tube straight. The tube is moved from one pair of rolls- I: to the next'by means of indexing chain Tensile strength lbs. per sq. in. 117, 200 Yield streng h do 103,200 Proportional limit -do- 96, 500 Elongation in 2" per cent 18. 5 Collapse pressure lbs. per sq. in. 6700 This increase in collapse pressure results in an. increase of approximately 38% in the depths to which the treated-casing can be set with a given factor of safety, permitting a. weight savings of approximately 25%. These amounts will vary somewhat according to the steel composition and temperature and amount of cold work, but in all cases the treatment should result in at least a 20% increase in settii' depths.

While one embodiment ...e invention has been shown and described, it will be apparent that other modifications and adaptations may be made without departing from the scope of the following claims.

I claim:

1. A method of enhancing the physical prop erties and resistance to collapse of pipe composed of steel containing between .15 and 50% carbon, .50 to 2.00% manganese, and .05 to .50% silicon comprising forming a pipe of said steel having a diameter of at least 3% larger than that desired in the final product, equalizing the temperature of said pipe at a point between 650 and 1000 F., and reducing the diameter of said pipe while 4 at said temperature to that desired in the final product.

2. A method of enhancing the physical prop erties and resistance to collapse of pipe composed of steel containing between .15 and 50% carbon, .50 to 2.00% manganese and .05 to .50% silicon comprising forming a pipe of said steel having a diameter at least 3% larger than that desired in the final product equalizing the temperature of said pipe at a point between 650 and 1000' F., straightening and reducing the diameter of said pipe to that desired in the final product while at sadi temperature and maintaining the pipe in straight condition while cooling.

3, A method of manufacturing seamless pipe, having enhanced physical properties and high resistance to collapse, composed of steel containing between .15 and 50% carbon and .50 to 1.75% manganese, which includes piercing a solid billet and performing tube rolling operations thereon to obtain a reeled and sized work-piece of a slightly smaller wall thickness and a diameter at least 3% larger than that desired in the final product, equalizing the temperature of said reeled and sized work-piece at a point between 650"v and 1000 F'. reducing the diameter to that desired and straightening same while at said temperature and maintaining said pipe in a straight condition while cooling.

4. A method of enhancing the physical properties and resistance to collapse of pipe composed of steel containing between .15 and .50% carbon and .50 to 2.00% manganese comprising forming a pipe of said steel having a diameter at least 3% larger than that desired in the final product, equalizing the temperature of said pipe at a point between 650 and 1000 F. and reducing the diameter of said pipe while at said temperature to that desired in the final product. 

